Fix USBPcapCMD on Windows XP

Since the initial extcap implementation, the USBPcapCMD was not working in
Windows XP. This is because minimum Windows version for TOKEN_ELEVATION is
Windows Vista.

Add a fallback administrator priviledge check for Windows XP.

USBPcapCMD/cmd.c

@@ -56,6 +56,39 @@ static BOOL IsElevated()
  {
  fRet = Elevation.TokenIsElevated;
  }
+ else
+ {
+ DWORD err = GetLastError();
+ if (err == ERROR_INVALID_PARAMETER)
+ {
+ /* Running on Windows XP.
+ * Check if executed as administrator by reading Local Service key.
+ */
+ HKEY key;
+ if (ERROR_SUCCESS == RegOpenKey(HKEY_USERS, "S-1-5-19", &key))
+ {
+ fRet = TRUE;
+ }
+ else
+ {
+ /* If we were executed with SW_HIDE then the runas window won't be shown.
+ * In such case pretend here that we are running as administrator so
+ * the process will fail (and not simply be waiting indefinitely
+ * without giving any clue).
+ */
+ STARTUPINFO info;
+ GetStartupInfo(&info);
+ if (info.wShowWindow == SW_HIDE)
+ {
+ fRet = TRUE;
+ }
+ }
+ }
+ else
+ {
+ fprintf(stderr, "GetTokenInformation failed with code %d\n", err);
+ }
+ }
  }
 
  if (hToken)